The present invention relates to a serial printer control circuit for driving/controlling a spacing motor and a line feed motor by using a single CPU.
In a conventional serial printer control circuit for driving/controlling a spacing motor for moving a head and a line feed motor by using a single CPU, the CPU generates timing signals for controlling the driving speeds of the spacing motor and the line feed motor by using a programmable timer, and performs speed control in accordance with interruptions to the CPU using the timing signals. In such speed control, if the line feed motor is controlled by utilizing a deceleration period of the spacing motor, which does not contribute to a printing operation, two interruptions must be simultaneously allowed. Such multiple interruptions cause an error in timing of driving the motors. For this reason, the line feed motor must be driven only after the spacing motor is stopped, thereby degrading operation efficiency of the printer.
On the other hand, in a serial printer control circuit for driving the line feed motor during a deceleration period of the spacing motor by using two CPUs, since the number of CPUs is increased, the number of their peripheral circuits are increased, resulting in an increase in cost.
A serial printer control circuit capable of eliminating the above drawbacks has been proposed. This control circuit includes a timer for setting a predetermined line feed amount in a counter and operating a motor for a period of time corresponding to the value set in the counter in a predetermined cycle. With this arrangement, line feed is performed by utilizing an operation period of the spacing motor and its deceleration period. However, since acceleration/deceleration control of the motor cannot be performed, it is difficult to efficiently operate the motor at high speed.